1. Technical Field
The present invention relates mainly to a liquid-filled type vibration absorbing device to be used for bearing the power unit such as an automotive engine or another vibration generating body in a vibration absorbing manner.
2 Background of the Invention
As a vibration absorbing device for bearing a vibrating body such as a car engine in a manner to prevent the vibration from being transmitted to the car body, there have been known various proposals: a liquid-filled type vibration absorbing device which is constructed such that the inside of a body portion having a vibration absorbing base made of a rubbery elastic member is partitioned into two upper and lower chambers by arranging a partition member and a diaphragm which form a wall of the chambers, such that these two chambers are filled up with a liquid to become liquid chambers, and such that these two liquid chambers are caused to communicate with each other through an orifice formed in the outer circumference of the partition member, so that a vibration attenuating function and a vibration insulating function may be performed by the fluid flowing effect of the two liquid chambers and by the vibration absorbing effect of the vibration absorbing base.
In Japanese Patent Laid Open No. 38015/1998, for example, there has been proposed a liquid-filled type vibration absorbing device which is constructed such that there is fitted, in a bottomed cylindrical body metal fixture acting as a lower mounting metal fixture to be jointed to the lower portion of a vibration absorbing base, an intermediate cylinder which is equipped with a diaphragm at its lower end portion, which a partition member fits in around its inner circumference and which has an orifice formed in its outer circumferential portion by which the intermediate cylinder is fitted in, thereby to form two liquid chambers and one air chamber in the body metal fixture.
In the vibration absorbing device thus proposed, the upper mounting metal fixture mounted on the vibrating body protrudes upward from the vibration absorbing base, and the bracket on the vibrating body is jointed and fixed on the upper mounting metal fixture. As a result, the bracket extending from the vibrating body is enlarged and restricted in its possible mounting structure thereby to the detriment of the light weight and the mountability.
On the other hand, the stopper metal fixture for regulating the large displacement of the upper mounting metal fixture is fixed on the upper end portion of the main body metal fixture and is formed into a cylindrical shape enclosing the vibration absorbing base and the upper mounting metal fixture. This makes it necessary to fix the bracket over the upper mounting metal fixture, as described above, and impossible to mount a larger upper mounting metal fixture than that stopper metal fixture.
As the vibration absorbing device including the upper mounting metal fixture having a mounting hole perpendicular to the device axis, on the other hand, there has also been proposed (e.g., Japanese Patent Laid Open No. 47416/1998) a vibration absorbing device which can fasten the upper mounting metal fixture transversely to the bracket on the vibrating body by means of bolts.
In the case of this vibration absorbing device, the upper mounting metal fixture can be fastened transversely to the bracket on the vibrating body side by means of the bolts so that the bracket can be made compact. However, the stopper member for regulating the large displacements of the upper mounting metal fixture in the vertical and longitudinal directions is fastened by means of bolts and nuts with respect to the support portion extending to both the front and back sides from the lower end portion of the lower mounting metal fixture. Thus, the stopper member is troublesome to mount and is hard to adjust according to its mounting mode.
The invention has been conceived in view of the background thus far described and has an object to provide a liquid-filled type vibration absorbing device capable of easily coping with a complicated mounting mode or limited size on the vehicle with a small number of components and capable of being easily assembled while retaining the necessary strength and enhancing the durability and the reliability.
According to the invention, there is provided a liquid-filled type vibration absorbing device in which a vibration absorbing base made of a rubbery elastic member is interposed between a holding cylinder opened at top and bottom belonging to a lower mounting metal fixture and an upper mounting metal fixture of a thick cylindrical shape having an axis perpendicular to the axis of the device, and in which there are arranged in the holding cylinder a diaphragm made of a rubber film facing the vibration absorbing base and a partition member for partitioning the space between the vibration absorbing base and the diaphragm into two compartments, thereby to form two liquid chambers communicating with each other through an orifice, comprising: an annular member having a flanged upper portion and a cylindrical lower portion and fixed on the outer circumference of the lower portion of the vibration absorbing base; and an intermediate cylinder jointed to the annular member, wherein the diaphragm is attached to the lower end portion of the intermediate cylinder whereas the partition member is fitted in the inner circumference of the intermediate cylinder, wherein the intermediate cylinder is fitted at its upper portion in the cylindrical lower portion of the annular member and is caulked and fixed at the outer edge portion of its upper end on the flanged upper portion of the annular member, thereby to form the liquid chambers individually between the partition member and both the vibration absorbing base and the diaphragm and to cause the two liquid chambers to communicate with each other through the orifice formed in the partition member, and wherein the intermediate cylinder is press-fitted in the holding cylinder.
According to the invention, the liquid-filled type vibration absorbing device is tentatively assembled in the liquid layer into the state where liquid is sealed internally, by fitting the upper portion of the intermediate cylinder having the diaphragm and having a partition member fitted therein in the cylindrical lower portion of the annular member at the outer peripheral portion of the lower portion of the vibration absorbing base, and by caulking and fixing the outer edge portion of the upper end of the intermediate cylinder on the flanged upper portion of the annular member. After this, the liquid-filled type vibration absorbing device can be assembled in the air by press-fitting the intermediate cylinder downward in through the top of the holding cylinder of the lower mounting metal fixture. By this process, the vibration absorbing device can be easily assembled. Especially, the intermediate cylinder acts as the supporting portion of the diaphragm and as the fixing portion for jointing the outer circumferential wall of the liquid chamber and the annular member at the vibration absorbing base, so that the construction can be simplified to reduce the number of components.
The liquid-filled type vibration absorbing device can further comprise a bridge-shaped stopper member arranged over and around the upper mounting metal fixture fixed on the upper portion of the vibration absorbing base, restricting this metal fixture""s large displacement, and the stopper member can be fixed at its two end portions by caulking a portion of the upper end edge of the holding cylinder of the lower mounting metal fixture. As a result, the stopper member can also be easily fixed while retaining a sufficient joint strength, to ensure the stopper action to suppress a large displacement.
The liquid-filled type vibration absorbing device is preferred to further comprise a stopper rubber integrated with the vibration absorbing base and attached to those portions of the upper portion and the side face of the upper mounting metal fixture, which correspond to the stopper member. Specifically, the upper mounting metal fixture can elastically abut against the stopper member through the stopper rubber thereby to prevent any hammering sound as might otherwise be caused by the abutment, to prevent noise.
The liquid-filled type vibration absorbing device can further comprise: a stopper portion extended from a portion of the flanged upper portion of the annular member for abutting against the upper mounting metal fixture when this metal fixture is much displaced downward, and the outer edge portion of the upper end of the intermediate cylinder can be caulked and fixed on the flanged upper portion of the annular member excepting the stopper portion. As a result, the intermediate cylinder can be caulked and fixed despite the presence of the stopper portion of the annular member.
In the liquid-filled type vibration absorbing device, the intermediate cylinder can include: an inner flange portion extended inward from the lower end portion of the intermediate cylinder and attaching the diaphragm to the inner circumference thereof; and a sealing rubber layer made integral with the diaphragm and attached to the inner circumference of the intermediate cylinder, and the partition member can be fitted liquid-tight by the sealing rubber layer at a position facing the inner flange portion. As a result, the two liquid chambers can be easily formed highly accurately in the intermediate cylinder, and the cover of the diaphragm can be omitted.
In the liquid-filled type vibration absorbing device, the partition member is preferably molded of a synthetic resin, aluminum or ceramics, and an orifice passage is formed in the outer circumferential portion of the partition member. As a result, the partition member can be easily fabricated, and the orifice for providing the communication between the two liquid chambers can be easily formed.
The partition member is preferred to have a plurality of through holes formed off center in the central plate portion thereof, and a rubbery movable valve is preferably disposed to confront the faces of the central plate portion for closing the through holes at the time of vibrations of a large amplitude. As a result, a high attenuation can be achieved at the time of vibrations of a large amplitude, and a low spring constant can be achieved at the time of vibrations of a small amplitude. Moreover, the space for forming the entrance/exit of the orifice can be retained without any problem.
The movable valve is preferred to include a pair of rubber plates so jointed to each other through the central plate portion of the partition member so as to come against the upper and lower faces of the central plate portion while leaving small clearances. The movable valve can be easily mounted, constructed and mounted.